The Pacific rainbow smelt (Osmerus dentex), also known as the Arctic rainbow smelt or cucumber fish in Japan, is a North Pacific species of fish of the family Osmeridae. The fish usually lives in marine and brackish environment, with a wide distribution from North Korea, Sea of Okhotsk to Bering Sea and British Columbia.[1] They are also seen in estuaries and coastal waters of European and Siberian shores of Arctic Ocean from White Sea to Chukota in Russian Far East.[2]
The Pacific rainbow smelt has a cylindrical elongated body shape, with lengths ranging between 14cmand16cmcm (06inchesand06inchescm).[3] The body color is mostly silver. They usually prey on plankton and squid.[2]
Pacific rainbow smelt usually return to their natal streams to spawn when the water temperature reaches 2 degree Celsius and above, but the degree of homing varies from one population to another and may be genetically controlled.[4] Movement to spawning grounds are usually made at night when the spawning group crowd together and move upstream.[5] The whole spawning usually lasts several hours each night for several nights.[6] Many spawned-out fish, especially males, die after spawning, but those that survive would spawn again in the following year.[7]